import math

x1, y1, x2, y2 = map(float, input().split())
line = (x2 - x1) ** 2 + (y2 - y1) ** 2
line = math.sqrt(line)
print(line)
 import math math x1, y1, x2, y2 = map(float, input().split()) x1 map(float, input().split()) map float input().split() ().split () input split y1 x2 y2 line = (x2 - x1) ** 2 + (y2 - y1) ** 2 line (x2 - x1) ** 2 + (y2 - y1) ** 2 (x2 - x1) ** 2 x2 - x1 x2 x1 2 (y2 - y1) ** 2 y2 - y1 y2 y1 2 line = math.sqrt(line) line math.sqrt(line) math.sqrt math sqrt line print(line) print line line = math.sqrt(line) math.sqrt(line) line x1, y1, x2, y2 = map(float, input().split()) map(float, input().split()) x1 y2 = map(float, input().split()) map(float, input().split()) y2 y1, x2, y2 = map(float, input().split()) map(float, input().split()) y1 x2, y2 = map(float, input().split()) map(float, input().split()) x2 line = (x2 - x1) ** 2 + (y2 - y1) ** 2 (x2 - x1) ** 2 + (y2 - y1) ** 2 line
import math

x1, y1, x2, y2 = map(float, input().split())
line = (x2 - x1) ** 2 + (y2 - y1) ** 2
line = math.sqrt(line)
print(line)

